A phenomenon that the image density of the unexposed portions of a silver halide photographic light-sensitive material is increased by development processing is said to be the occurrence of a "development fog". Usually, the development fog is more liable to occur as the sensitivity of the photographic light-sensitive material is higher. Also, when a photographic light-sensitive material is stored for a long period of time or a photographic light-sensitive material is stored under the condition of a high temperature and a high humidity, a fog is also liable to occur. Furthermore, when a photographic light-sensitive material is subjected to high-temperature processing or high-active processing for shortening the processing time, the development fog is very liable to occur. Since such occurrence of a development fog causes photographic property deterioration such as lowering of an image contrast, etc., it is necessary to restrain the occurrence of the development fog as completely as possible.
For restraining the occurrence of the development fog, a method of adding an additive called an antifoggant to a photographic light-sensitive material or a developer has conventionally been employed. Such antifoggants are explained in detail, e.g., in Birr, Stabilization of Photographic Silver Halide Emulsions, published by Focal Press, 1974. Also, various compounds such as nitrogen-containing heterocyclic compounds are already proposed as antifoggants.
However, the compounds having a strong antifogging action have the problems that the compounds lower the sensitivity of photographic light-sensitive materials, soften the gradation of light-sensitive materials, or hinder the absorption of sensitizing dyes to silver halide grains to lower the spectral sensitivity, etc. Thus, the development of strong antifoggants giving less such problems has been desired.
Conventional antifoggants are mostly nitrogen-containing heterocyclic compounds, in particular, benzotriazole antifoggants are known and described in JP-B-60-29390 (corresponding to DE 2727194), JP-B-60-29391 (the term "JP-B" as used herein means an "examined published Japanese patent application") and U.S. Pat. No. 3,671,255. 1,2,3-triazole antifoggants having a condensed heterocyclic ring are disclosed, for example, in U.S. Pat. Nos. 3,554,757 and 4,307,186, and examples of such antifoggants, such as 1H-1,2,3-triazoro[4,5-b]pyridine antifoggants are also described in JP-A-3-138639 and JP-A-4-97348 (the term "JP-A" as used herein means an "unexamined published Japanese patent application").